The 83-year-old victim was walking her dog by the lake when the incident happened just before 3.30pm on Friday April 15.
Police said after her friend challenged the woman about picking flowers, the suspect became verbally abusive and threatened to throw the pensioner’s dog in the lake.
A spokesman for Pontefract and Knottingley Neighbourhood Policing Team, said: “The victim bent down to pick her dog up when the female suspect assaulted the elderly woman, causing injury.
“This is a cowardly attack and we would like to reassure everyone that these attacks are not common and we have stepped up patrols in the area. If you have any information that could help us, please call 101 or CrimeStoppers anonymously on 0800 555 111.”